Controlling a stepper motor with computer

[Malhoosh]

Hello all,

I want to control a stepper motor using the computer to track the motion of a teacher in a classroom. For example i might put a webcam on the motor and control the motor to keep the camera pointing to the teacher.

The teacher will be using a pen with an IR led at its top so that another IR camera locates where the teacher is on the board and this information is used to direct the stepper motor.

If I was able to convey my idea to you, my questions are:

1- Will a stepper motor be efficient for such a job ? I mean will it be accurate enough and give a fast response ?

2- What materials will I need to control the stepper motor in this case ? Any links that can be useful ?


Thank you

 

[Fish4Fun]

For a walk through try this:

http://www.cs.uiowa.edu/~jones/step/

Typical stepper motors are 1.8 degree per full step (200 steps per revolution). Various controllers allow 1/2 step, 1/4 step and higher resolutions for both unipolar and bipolar configurations. There are stepper motors with higher and lower step counts available. A typical PC controlled stepper motor involves a controller that interfaces with the PC and a driver that supplies the current to the stepper motor.

Stepper motors generally drive either a lead screw, belt or gear. In most cases accuracy, torque and speed are design parameters that can be achieved. With a 36:1 gear reduction on a 1.8 degree stepper motor, you could achieve 1/400th of a degree accuracy with a 1/2 step controller. It would be fairly trivial to rotate your camera with this precision @ over 20RPM if you decided that was required.

Fish

 

[vk6kro]

Have you considered servo motors?

These cover a rotation of 90 degrees but do it very quickly (much faster than stepper motors). They are used for radio controlled models and robots so they are available quite cheaply at Hobby stores.

They are driven by a pulse stream of 0.75 mS to 2.25 mS (depending on the angle required) every 20 mS.